pure mathematics. Perhaps he did not find in them the encouragement he hoped. For whatever reason, from this time he began to devote his attention to mechanical and practical investigations. Going from Paris by way of Hamburg to Rostock, in the north of Mecklenburg, he writes from there to Benzelius. Sept. 8, 1714,—
"I am very glad that I have come to a place where I have time and leisure to gather up all my works and thoughts, which have hitherto been without any order, and are scattered here and there upon scraps of paper. I have always been in want of a place and time to collect them. I have now commenced this labor, and shall soon get it done. I promised my dear father to publish an academical thesis, for which I shall select some inventions in mechanics which I have at hand. Further, I have the following mechanical inventions either in hand or fully written out, namely,—
"1. The plan of a certain ship, which, with its men, can go under the surface of the sea, wherever it chooses, and do great damage to the fleet of the enemy.
"2. A new plan for a siphon, by which a large quantity of water may be raised from any river to a higher locality in a short time.
"3. For lifting weights by the aid of water and this portable siphon, with greater facility than by mechanical powers.
"4. For constructing sluices in places where there is no fall of water, by means of which entire ships, with their cargoes, may be raised to any required height within an hour or two.
"5. A machine driven by fire, for throwing out water; and a method of constructing it near forges, where the water has no fall, but is tranquil.
"6. A draw-bridge, which may be closed and opened within the gates and walls.
"7. New machines for condensing and exhausting air by means of water. Also a new pump acting by water and mercury, without any siphon; which presents more advantages and works more easily than the common pumps. I have also, besides these, other new plans for pumps.
